Means for increasing frequency



1950' F. s. LOGAN 2,517,396 a;

MEANS FOR :[NCREASING FREQUENCY Filed on. 1, 194a 2 Sheets-Sheet 1 IN VEN TOR.

s- 1, 1950 F. G. LOGAN 2,517,396

MEANS FOR INCREASING FREQUENQY Filed'oot. l, 1948 2 Sheets-Sheet 2JNVENTOR. 5 mm 6T [06AM Patented Aug. 1, 1950 MEAN S FOR INCREASINGFREQUENCY Frank G. Logan, Kirkwood, Mo., assignor to VickersIncorporated, Detroit, Mich., a corporation of Michigan ApplicationOctober 1, 1948, Serial No. 52,210

10 Claims. 1

This invention relates to improved methods and means for increasing thefrequency of an electric current from a comparatively low value to ahigher value which may be man times the value of the initial frequencyfrom which the increased frequency is derived.

Although there are a number of different ways to produce highfrequencies, they require special apparatus which is not usuallyavailable in electrical installations or plant equipment. One object ofthe present invention is to provide a method for deriving high frequencycurrents from sources of current which are commonly available. Anotherobject is to provide. apparatus for accomplishing this purpose which maybe conveniently manufactured. A further object is to provide apparatuswhich avoids the necessity of using tubes or other devices which arelikely to deteriorate or break down in operation and which require spareparts to be kept on hand for replacements. Thus a further object is toprovide apparatus which will be durable and dependable under longcontinued use. Other objects and advantages will be understood from thefollowing description and accompanying drawings.

Fig. 1 is a diagram illustrating one embodiment of the invention; andFigs. 2 to 5 are explanatory charts.

Before considering the disclosures of Fig. 1, some general explanationsare desirable as to the method employed and the mode of operation. Theinvention is based upon the production and utilization of thirdharmonics. Fig. 2 shows a hysteresis loop of a magnetic core and is of aform which is a desirable one for explaining the derivation of thirdharmonics. When the loop is more narrow it tends to produce a higherorder of hai 'monics in the exciting current. In Fig. 2 the abscissas Hrepresent the field intensity and for a given structure represent theexciting current. Other factors affecting H are the number of turns inthe exciting winding and the mean length of the magnetic path and theseare fixed for a given structure. The ordinates B of Fig, 2 represent theflux density of the core and for a given structure and frequency is afunction of the impressed electromotive force. The flux density alsodepends upon the cross-sectional area of the magnetic core and for agiven structure this is fixed. It may be assumed for present purposesthat a core structure and winding have been designed as determined bythe above-mentioned factors for producing a hysteresis loop of thegeneral form shown in Fig. 2.

If an electromotive force having a sine wave form be impressed on theexciting winding or primary winding of a transformer, the circuit of thesecondary winding being open, the resulting flux wave will also besinusoidal but will be displaced in time from the exciting current. If asine I wave of electromotive force be applied to a structure such aswould produce a hysteresis loop as shown in Fig. 2, the exciting currentwave would be somewhat distorted in order to produce the flux in thecore. This is generally represented in Fig. 3 where the dotted line Crepresents the distorted current wave. This wave may be resolved byFourniers analysis to obtain essentially a fundamental sine wavedesignated as F in Fig. 3 and a sine wave designated by T in Fig. 3 of afrequency which is triple that of the fundamental wave and commonlyreferred to as the third harmonic. The amount of the third harmonicproduced depends upon the shape of the hysteresis loop which dependsupon the magnetic material in the core and the flux density imposedthereon. Although higher harmonics also appear in the current wave, thethird harmonic predominates.

If three similar single phase transformers or a three-phase transformerbe supplied from a: three-phase source to their respective primarieswith their primaries connected in Y and their secondaries connected indelta, a third harmonic will be developed in the delta connection. As--suming balanced conditions, the fundamental voltage across an opencorner of the delta will.

be zero. The only voltage then appearing will be due to harmonics,primarily the third. The three fundamental voltages in the delta will bedisplaced and the third harmonic will have the same relativedisplacement with reference to.

have their phases displaced 40 as assumed, the

sets be superimposed there results three phases of sine waves displacedfrom each other 120 and each having triple the frequency of each of. thethree-phase sources. This is shown in Fig. where the full line shows onephase of the third harmonic, the dotted line the second phase and thedot and dash line the third phase. The loads on the three-phase outputof the secondaries can be connected in Y or in delta depending upon theparticular application. Also by repeating the method of tripling thefrequency as already described in another stage of multiplication, athird harmonic of athird harmonic may be obtained giving nine times theoriginal supply frequency. An additional stage will result intwenty-seven times the original frequency and so on.

The three-phase sources having relative phase displacements of 40 can bederived from a single three-phase source by using phase adjusters forobtaining the relative displacement. The 40 degree displacedthree-phasesources are equivalent to a nine-phase source and therefore aminephasegenerator may be used as a single source. The nine phases may be derivedalso from a three-phase Y and zig-zag transformer connection and alsofrom a three-phase delta autotransformer connection with tappedconnections, as later explained.

Referring to Fig. 1, a nine-phase generator I is indicated as theinitial source provided with a field winding Ia energized from aseparate exciter lb. Three sets of similar three-phase transformers, orthree groups of three single phase transformers have their primarywindings connected in Y and are supplied from the ninephase generator.The primary windings 2 of the upper group are connected to the terminalsof the generator to cause the phase displacement of the electromotiveforces supplied thereto to be 120 apart. The primary windings 3 of themiddle group are similarly connected to the generator and theelectromotive forces supplied thereto are displaced 40 relatively to theelectromotive forces supplied to the upper group. The primary windings 4of the lower group are similarly connected and its phases are displaced40 from those of each of the other groups. This relative phasedisplacement of the electromotive forces supplied to the three groups isindicated by a corresponding angular displacement of the three groups onthe drawing. The secondary windings 2a of the upper group are connectedin delta except at one.

corner or apex for supplying the third harmonic current to the nextstage. The secondaries 3a of the middle group and 4a of the lower groupare similarly connected. If the. frequency of the electromotive forcesof the generator be 400 cycles per. second, it is apparent from theforegoing explanations that the frequency of the current output from thesecondaries of the three groups will be 1200. Three capacitors I areshown connected across the lines supplying the primary windings of eachgroup for improving the power factor of the energy supplied to eachgroup; and three capacitors 8 are shown connected in series in the linessupplying the primary windings of each group to compensate for reactancein these windings.

V A nine phase source is next derived from the output of the secondariesof the first stage. A

three-phase Y transformer connection is shown havingv the main windings5, 5a and 51). They are respectively supplied with the third harmoniccurrents from one terminal of each group of secondaries 2a, 3a and 4a,theremaining terminals thereof being connected to a common connection 6.Three capacitors 1a are connected across the circuits of thesesecondaries for improving the power factor of the energy supplied to thesucceeding stage; and three capacitors 8a are connected in series in thecircuits of the secondaries to compensate for reactance in the primarycircuits of the next stage.

In order to derive the nine phase from the Y- connected transformerwindings 5, 5a and 5d, the zig-zag connection as shown in Fig. 1 isutilized. The secondary winding 9 is related to the primary winding 5bfor generating an induced electromotive force therein corresponding tothe phase of the primary 5b but displaced therefrom. 180.

I nected to a tap in the primary winding 5 at such a location as willresult in the winding 9 combined with a portion of the winding 5delivering an electromotive force 40 displaced from that of the winding5 and of the same value. Thus a line drawn from the mid-connection ofthe Y- connected primaries to the outside terminal of the winding 9 willrepresent the phase and value of the electromotive force delivered fromthe outside terminal of the winding 9. The secondary winding 9a isapplied in relation to the winding 5b to receive an inducedelectromotive force therefrom and is connected at a location in thewinding 5a such that the combined forces of the winding 90. and innerportion of winding 5a will give a resultant electromotive force at theoutside terminal of winding 9a displaced 40 in phase from that ofwinding 9 and from that of winding 5a and having an electromotive forceequal to that of the primary Y-connected windings. In the same mannerthe winding 9b is located in relation to the primary winding 5 andconnected to an intermediate point of winding 5a to deliver anelectromotive force equal to that of the primaryv windings and displaced40 from the electromo-.

tive force of winding 5a. The secondary winding is likewise related tothe winding 5 and connected to an intermediate point in the winding 5bfor obtaining another resultant electromotive force displaced 40 fromthat of the output from winding 9b and winding 5b. Likewise the winding9d is related to the primary winding 5a and connected to an intermediatepoint of the winding 5b; and similarly the secondary winding 9e isrelated to the primary winding 5a and connected to an intermediate pointin the winding 5. Thus the nine phases of electromotive force having aphase displacement of 40 are derived from the three-phase Y-connectedprimaries 5, Scand 5b. The secondary windings 9a to 9e are shown,

displaced from their relationship to their respective primary windingsfor clearness but their angular positions correspond with that of theprimary windings to which they are related.

At the middle of Fig. 1 is shown another three groups of transformers,each group having their primary windings respectively connected inproper phase relationship to the nine terminals of the zig-zagtransformer connection already described. Thus the primary windings I0of the upper group are connected in Y and their outside terminals to theprimary windings 5, 5a and 5b. The primary windings ll of the middlegroup are connected in Y with their outside terminals to the windings 9,9b and 9d. The primary windings l2 of the lower group are connected in Yand their outside terminals connected respectively to the outsideterminals of the windings 9a, 90 and 9e. The secondary windings Illa,Ila and 12a of each in the drawing. 4 I Ia of the upper. group oftransformer windings at the right of group-are connected indelta in thesame manner as described with reference to the secondaries of the threeleft-hand groups. The frequency of'the. third harmonic currentsdelivered from the secondary windings Illa, Ha and 12a will be threetimes that delivered from the secondaries 2a, 3a and 4a, or 3600 cyclesper second under! the assumption of an initial .400 cycles.

.Atathe middle right-hand portion of Fig. 1 are shown threeauto-transformer windings I3, I30. and [3b connected in delta.- Oneterminal from the delta connected secondary ,windings a is connected tothe junction between the windings l3yand I31); one terminal of the deltaconnected secondary windings I la is connected to the junction betweenthe windings l3 and 13a; and one terminal of the delta connectedwindings l2a is connected to the junction between the windings 13a and13b. The remaining terminals of the delta connected secondaries areconnected to a common neutral connection l4. Capacitors 1b are connectedacross the lines of the delta connected secondaries similarly to thecapacitors 1a; and capacitors 8b are connected in series in the circuitsof the secondaries similarly to the capacitors 8a for the purposespreviously stated.

The delta connected auto-transformer windings l3, l3a and [3b areutilized for deriving therefrom nine phases of electromotive force dis;placed and show another method of deriving nine phases from thatpreviously discussed. At the right of these windings are shown threegroups of Y open-delta connected transformer windings having primarywindings l5, l6 and I1, each being Y-connected and secondary windingsl5a, I Be and Ila. The three primarywindings l5 are connectedrespectively to the apex junc-- tions of the windings I3, l3a and Bogiving a displacement in phase of the electromotive forces applied tothe windings IS. The windings I 6 0f the next lower group are connectedto intermediate points in the windings l3, l3a and l3b respectively atlocations which result in applyingelectromotive forces to the windingsl6 displaced 120 from each other and displaced 40 respec-= tively fromthe electromotive forces applied to the windings I5. The lower group ofprimary windings I! are connected respectively to inter-- windings I5 isgreater than that applied to the windings l6 and I! and in order toimpose equal values of electromotive forces on the secondary windings ofeach group, this may be accom- The phase differ-- The. value. of theelectromotive forces applied to the primary plished by providing acorrespondingly greater number of turn in the primary windings l5thaniI, as indicated in the primary windings l6 and l The secondary windingsFig. 1 are connected in open delta and the secondary windings Mia andIla of the middle and; lower groups are similarly connected. One ter-.

ings are ccnnected in openfdelta to a load circuit.

asindicated. Capacitors 1c are connected across the lines of the deltaconnected secondaries; and capacitors are connected in series in thecircuits of the secondaries for the purposes previously described.

The frequency of the current delivered to the primary windings i9 isthree times the frequency derived from the previous stage ofmultiplication and as this was assumed to be 3600 cycles per second, thefrequency of the current delivered to the primary windings I9 is 10,800cycles.

The Y open-delta transformer windings l9 and I9a serve to again triplethe frequency of the current supplied thereto which results in thecurrent supplied to the load having afrequency of 32,400 cycles, or 81times the assumed 400 cycle frequency of the initial supply. A capacitor20 is shown connected in series in the load circuit for compensating forreactance in the circuit. A saturating reactor having a closed magneticcore 2! and having a reactive Winding 2| (1 connected across the loadcircuit is provided for maintaining an approximately constant current inthe output circuit of the series connected secondary windings; otherwisethe voltage would change considerably with change of load as theapparatus is not self-regulating. This reactor is maintained atsaturation resulting in. a pronounced change of current through itswinding under small changes of the applied voltage. Thus upon increaseof the load and a small drop in voltage of the output circuit, thecurrenttaken by the reactor winding Zia is con siderably decreased..When the load is decreased,v

, the current taken by the winding 21a is increased correspondingly.

In this manner the reactor serves to maintain an approximately constantcurrent in the output circuit regardless of the change in load. Insteadof usinga saturating reactor, any other suitable device or resistorhaving a non-linear relationship of current change with reference to theapplied voltage may be used Although four multiplications of the initialfrequency have been disclosed, a lesser number may be utilized or, wheredesired, additional stages of multiplication may be used. In tests ofthis apparatus the volt-ampere efficiency was found to be approximately20% per stage Without the use of compensating capacitors. The powereiiiciency depends on the losses in the core material and in the copper.The use of very thin laminations and of high permeability core materialsaids in improving the power efficiency. The volt-ampere efficiency isimproved by the use of capacitors in the input circuits to each stage,as

. indicated in Fig. 1.

It will be appreciated from the foregoing disclo'sures thatthe threegroups or sets of Y open' delta connected transformer windings serve todeliver three third harmonic currents out of for supplying another threegroups or sets of Y open-delta connected transformer windings forobtaining an additional stage of multiplication. The output currents oftripled frequency from any of thegroups may be applied directly to andutilized in a three-phase consumption circuit or to three single phasecircuits when so de sired or applied to a single set of three-phasetransformer windings having Y-connected pri maries and open-delta orseries connected secondaries supplying a single-phaseconsumption circuitgiving a further tripling of the frequency as in the last stage of Fig.1,

' Instead of using three groups energized-from a nine-phase supply, adifferent number of groups could be used according-to the number ofphases availed of for supplying the different groups. Also, instead ofusing a nine-phase generator as the initial source shown herein forconvenience, the desired number of phases could be derived from atwo-phase supply, a three-phase supply and so on, using any of the knownmethods for deriving therefrom the desired number of phases. And insteadof using three-phase transformer windings in Y open-delta connection ineach group, a different number of phases could be used having theprimary windings connected in star to a common neutral and the secondarywindings of each group'connected in series to their output circuitsprovided that the resultant of the fundamental electromotive forces ofsuch output circuits is substantially zero.

Although a particular embodiment of this invention has been disclosed,it will be understood that various modifications may be made withoutdeparting from the scope thereof.

I claim: I

1. Apparatus for increasing the frequency of electric currentscomprising a plurality of groups of polyphase transformer windings, eachof said groups having its primary windings connected in 3 star and itssecondary windings connected in series with each other to theirrespective output circuits, means for supplying polyphase currents toeach of said groups, the phase of the currents supplied to each of saidgroups being displaced 3 from the phase of the currents supplied to eachof the other groups, and polyphase transformer windings having theirprimaries connected in star and respectively connected to said outputcircuits and having their secondaries connected in series with eachother for supplying an output circuit.

2. Apparatus for increasing the frequency of electric currentscomprising three groups of three-phase transformer windings, eachofsaidfi groups having its primary windings connected in Y and itssecondary windings connected in series with each other to theirrespective output circuits, means for supplying three-phase currents toeach of said groups, the phase of the currents supplied to each of saidgroups being displaced from the phase of the currents supplied to eachof the other groups, and three-phase transformer windings having theirprimaries connected in Y and respectively connected to said outputcircuits and having their secondaries connected" in series with eachother for supplying an output circuit.

3. Apparatus for increasing the frequency of electric currentscomprising a plurality of groups 6 of polyphase transformer windings,each .of said groups having its primary windings connected in star andits secondary windings connected in series with each other to theirrespective output,

circuits, means for supplying polyphase currentsis to the primarywindings of each group, said polyphase currents supplied to each groupbeing displaced in phase from the currents supplied to each of the othergroups, polyphase transformer windings respectively supplied withcurrent from the output circuits of said groups, means for derivingcurrents from said last named polyphase transformer windings having anincreased number of phases, and a second plurality of groups ofpolyphase transformer windings, each of the latnected in series witheach other to their respective output circuits, the primary windings ofeach of said second groups being connected to receive out of phasecurrents from said last namedmeans and the currents supplied to each ofsaid second groups being displaced in phase from the currents suppliedto each of the other second groups 4. Apparatus for increasing thefrequency of electric currents comprising three groups of three-phasetransformer windings, each of said groups having its primary windingsconnected in Y and its secondary windings connected in series with eachother to their respective output circuits, means for supplyingthree-phase currents to the primary windings of each group. saidthree-phase currents supplied to each group being displaced in phasefrom the currents supplied to each of the other groups, three-phasetransformer windings respectively supplied with current from the outputcircuits of said groups, means for deriving nine-phase currents fromsaid last named three-phase transformer windings, each of the lattergroups having its primary windings connected in Y and its secondarywindings connected in series with each other to their respective outputcircuits, the primary windings of each of said second groups beingconnected to receive three-phase currents from said last named means andthe currents supplied to each of said second groups being displaced inphase from the currents supplied to each of the other second groups.

5.- Apparatus for increasing the frequency of electric currentscomprising a plurality of groups of polyphase transformer windings, eachof said groups having its primary windings connected in star and itssecondary windings connected in series with each other to theirrespective output circuits, means for supplying polyphase currents toeach of said groups, the phase of the currents supplied to each of saidgroups being displaced from the phase of the currents supplied to eachof the other groups, and capacitors respectively connected in series inthe input circuits to said groups.

6. Apparatus for increasing the frequency of electric currentscomprising a plurality of groups of polyphase transformer windings, eachof said groups having its primary windings connected in star and itssecondary windings connected in series with each other to theirrespective output circuits, means for supplying polyphase currents toeach of said groups, the phase of the currents from the phase of thecurrents supplied to each of the other groups, capacitors respectivelyconnected in series in the input circuits of said groups, and capacitorsrespectively connected across said input circuits.

8. Apparatus for increasing the frequency ofelectric currents comprisinga plurality of groups of polyphase transformer windings, each of saidgroups having its primary windings connected in star and its secondarywindings connected in series with each other to their respective outputcircuits, means for supplying polyphase currents to each of said groups,the phase of the currents supplied to each of said groups beingdisplaced from the phase of the currents supplied to each of the othergroups, polyphase transformer windings having their primaries connectedin star and respectively connected to said output circuits and havingtheir secondaries connected in series with each other for supplying anoutput circuit, and a capacitor connected in series in said outputcircuit.

9. Apparatus for increasing the frequency of electric currentscomprising a plurality of groups of polyphase transformer windings, eachof said groups having its primary windings connected in star and itssecondary windings connected in series with each other to theirrespective output circuits, means for supplying polyphase currents toeach of said groups, the phase of the currents supplied to each of saidgroups being displaced from the phase of the currents supplied to eachof the other groups, polyphase transformer windings having theirprimaries connected in star and respectively connected to said outputcircuits and having their secondaries connected in series with eachother for supplying an output circuit, and a device connected acrosssaid output circuit for use in parallel with the load on the circuit,

' of the other groups, polyphase transformer windings having theirprimaries connected in star and respectively connected to said outputcircuits and having their secondaries connected in series with eachother for supplying an output circuit, and a saturable reactor connectedacross said output circuit for use in parallel with the load on thecircuit.

FRANK G. LOGAN.

REFERENCES CITED UNITED STATES PATENTS Name Date Huge Mar. 2, 1948Number

